For many years, farmers, highway departments, and others have been cutting large expanses of weeds and grass with tractor-drawn field mowers utilizing some sort of reciprocating sickle bar. It has been found that these machines are most efficient in cutting swaths of grass without leaving behind uncut areas. Other machinery, including combines and windrowers utilize the same sort of reciprocating sickle action and to simplify the application reference will be made to a sickle bar cutter throughout.
All of these machines perform satisfactorily as long as the sickles remain in place on the reciprocating bar. However, when the mower runs into small hidden obstructions such as tree stumps, rocks, or even small trees, the sickles have a tendency to break or jam and pop loose from their rivet mounting. Once this occurs, the mower or other device will fail to cut the area once covered by the damaged sickle so that an uncut row is left behind the mower. This is obviously undesirable; the mower must retrace its path with a different area of the bar to cut the uncut trail. Furthermore, some of the uncut grass will jam the sickle bar action. The best way to eliminate the problem is to replace the sickle on the reciprocating bar so that it will once again cut.
At least one device has been developed to replace sickles while the mower remains in the field. This device is disclosed in Olsen U.S. Pat. No. 2,955,494 issued Oct. 11, 1960. This device consists essentially of a hanger member supporting a see-saw bar with relatively large masses at either end of the bar. The heavier mass holds an end of the bar down which raises the other end with the smaller mass and the rivet post against the new rivet. The mass of each end helps absorb the shock of the hammer as the new rivet is peened against the rivet poast.
It has been found that the Olsen device is inconvenient for carrying along on a tractor or other farm machinery due to its bulk and weight. Also, due to the relatively complex structure and the amount of metal used in the device, it is undesirable from a cost standpoint as well.
Applicant has succeeded in developing a rivet anvil which will support the rivet as it is peened but with a much simpler structure using much less mass, making the device much more convenient to carry and relatively inexpensive by comparison. Applicant's device also retains the other advantages of the Olsen invention including freeing both hands of the operator for positioning the sickle and rivet while peening.